Original post updated.

MMJuno wrote:

Probably because it was printed at the Common slot in Portal 2nd Age, so the card itself exists at both Common and Uncommon.

I realize that, check update.

Righteous Charge (GTC, Uncommon) is included in the search results, when using parameters Type("is one of"="Sorcery"), Rarity("is one of"="common"), Color("exclusively one of"="white").
Using Chrome Version 31.0.1650.57 m

Update: This is searching my inventory having only the uncommon Gatecrash version added.